Internal combustion engines operating on a two-cycle principal have traditionally been arranged so that fuel is delivered into an incoming air supply. The fuel and air mixture passes into a crankcase chamber for crankcase compression, and is then delivered through a scavenge passage to a combustion chamber of the engine for combustion therein.
As is well known, in the operating cycle of a two-cycle engine, an exhaust port leading from the combustion chamber is open during at least part of the time the scavenge passage is open. Thus, exhaust along with a portion of the air and fuel charge delivered through the scavenge passage flows through the exhaust port into the exhaust system.
In this arrangement, and especially at low engine speeds, a large amount of fuel must be added to the air to compensate for the flow of fuel through the cylinder and directly out the exhaust port. Supplying excessive fuel, however, is costly and can result in stalling of the engine. In addition, the quantities of fuel flowing into the exhaust may foul a catalyst positioned in the exhaust system.
As one attempt to solve the above-stated problems, some two-cycle engines are arranged to have fuel directly injected into the combustion chamber. A fresh air charge is supplied to each combustion chamber through the crankcase and a scavenge port Once air is supplied to the combustion chamber and the exhaust port is closed, a fuel injector injects fuel directly into the combustion chamber for mixing with the air.
This arrangement has the benefit that little of the fuel flows unburned into the exhaust system, and the amount of fuel supplied to each combustion chamber may be closely controlled. On the other hand, in order for this system to work, fuel must be supplied to the fuel injector under high pressure. Thus, these systems have a fuel supply which includes a fuel tank and a high pressure pump for pumping fuel from the tank and supplying it under high pressure to the fuel injector.
In some instances, mechanically driven pumps have been used for this purpose. In these situations, fuel is delivered to an injector which injects fuel into the combustion chamber when the pressure in a pressure circuit exceeds a predetermined pressure. This arrangement is very complex and does not permit complete control over the timing of the injector.
More commonly, the high pressure pump is electrically operated. These pumps, however, require complex circuitry for their control. When the engine is used, for example, to power an outboard motor, the circuitry consumes precious space within the motor cowling.
A fuel supply system for delivering fuel from a fuel source to a combustion chamber of an engine through a fuel injector at high pressure and without the above-stated problems is desired.